1. Field of the Invention
This invention relates generally to reinforced hose, more particularly to crimped or swaged couplings for reinforced hose, and specifically to crimped or swaged couplings for cable or wire rope reinforced hoses.
2. Description of the Prior Art
Typically, blow out preventers (BOPs) are used when oil or gas wells are drilled. Blowout preventers are hydraulically controlled valves used to control well kicks and prevent blowouts. A single well may have three or more preventers, stacked one on top of the other. On a land rig, the stack is located beneath the rig floor at ground level. On an offshore rig the BOP may be located on the seafloor. The top preventer on a stack is usually an annular preventer. The annular preventer may be used to completely seal off the drill well annulus (the space between the drill pipe and the borehole). It also can seal off a drill hole that has no pipe. Below the annular preventer are additional controls called ram preventers. The ram preventers are designed to fit around various sizes of drill pipe to hold, close or seal the mud return annulus. Blind rams are used to seal off an open hole. Pipe rams can seal off the drill pipe and the hole.
Rock formations may contain pockets of oil, gas or water under extremely high pressures. A drilled hole may intersect any of these. When any of these high-pressure fluids enter the hole it is referred to as a “kick.” When a well kicks, there are several options for handling the kick. The resulting downhole pressure can be cycled out through the BOP system's manifolds at the surface. Alternatively, an attempt can be made to force the downhole fluid back into the formation, such as by pumping drilling fluid under high pressure into the hole through a choke and kill line. Choke and kill hose is used for this purpose. A final option is to pump in cement, seal off the hole and abandon the drilling operation.
Flexible reinforced pipes and hoses are currently used in Choke and Kill applications on oil rigs. These hoses/pipes and couplings are designed to act as a conduit for the pumping of mud (drilling waste) back down into a well head to block the well head fluid against oil, methane gas and noxious chemicals such as Hydrogen Sulphide, at extreme temperatures and pressures. These hoses typically comprise a rubber polymeric tube and are reinforced using multiple layers of “close wound”, high tensile plated steel cables (or wire rope) to withstand flexing and high pressures encountered in oil field and offshore operations. This cable reinforcement is typically wire stranded rope, which is typically interchangeably referred to as “cable” and/or “wire rope.” These hoses also typically include multiple layers of fabric reinforcement disposed under the hose cover, which may be a modified nitrile resistant to abrasion, corrosion, cutting, gouging, oil and weather.
Prior crimped or swaged couplings 100 for choke and kill hose applications typically employ ridged ferrule 101 and barbed stem fitting 102, such as shown in prior art FIG. 1. This ferrule and stem are typically welded together (103), leaving an opening, which accepts hose 105. Baldwin, et al., U.S. Pat. No. 7,338,090, employs a “waved” ferrule and stem that joins an end connector to the coke and kill hose. This ferrule and stem are also welded together at the coupling end, leaving an opening, which accepts the reinforced hose. However, in Baldwin, et al., the lands of the ferrule and high points of the stem have a sinusoidal shape, providing the aforementioned “wave.” This wave bends the cable/wire rope reinforcement in the hose but does not significantly distort the cables. The stem is designed to support the hose which is inserted over it and under the ferrule. The ferrule is swaged or crimped down onto the hose to provide compressive forces, sealing the hose against the stem and retaining the hose in the coupling. For use with this sort of coupling the cover of the hose is skived (i.e. stripped away) so that the ferrule is able to press down on the cable reinforcement, directly, without the need to penetrate the rubber cover. Still, in designs like Baldwin coupling retention is dependent upon the properties of the rubber to provide a reaction force to compression preventing the cable reinforced hose slipping out of the couplings, such designs may lose their capability at elevated or reduced temperatures where the properties of the rubber layers change and may provide less support.
Other approaches to retaining a fitting on a cable reinforced hose call for unraveling reinforcement cable extending from an end of the hose and welding individual elements (cables) to a coupling. Problematically, such approaches are time consuming, expensive and require qualified welders.
API (American Petroleum Institute) 16 C standards testing includes testing such as a thirty-day exposure test at 20,000 psi working pressure, at elevated temperature, for choke and kill hose assemblies. When choke and kill hose assemblies employing the above-described couplings are exposed to theses conditions it was found that the hose-coupling interface is susceptible to temperature extremes. The properties of the rubber material change at elevated temperature and as a result the rubber can flow and allow the compressive forces in the coupling ferrule to drop. This can result in loss of coupling retention which is not acceptable in choke and kill, or similar, applications.